1. Field of the Invention
The present invention relates to a finger printing-based location tracking system, more particularly, to a location tracking system and the method thereof for storing location information based on a finger printing to estimate a tag position and a moving path unaidedly and building up a location database when building up location data per signal intensity in the location tracking system.
2. Description of the Related Art
An RLTS (Real Time Location System) is a technology of tracking in real time a position of a person or equipment in a limited space such as a construction site, an amusement park, and a hospital. Such a location system may be divided into a triangulation and a finger printing technique in view of measurement techniques. The triangulation refers to a technique of obtaining a distance to three known points thereby to acquire an error-minimized position, in which each distance can be achieved by converting a TDOA (Time Difference of Arrival) of electric waves to a length or an RSSI (received signal strength indicator) of signals to a corresponding distance.
Furthermore, a finger printing technique makes reference to recording a characteristic of signals (intensity of signals, etc) at a specific position for a database and searching for characteristics of a signal obtained at any position from the database, for estimation of a current position. Such a finger printing technique may be divided into two procedures. That is, a pre-process procedure that records characteristics of a signal, and maps it to a position atlas to build up a database, and a post-process procedure searching for a signal's characteristic from a database.
Herein, a real time location system mainly employs a wireless LAN or on RFID (radio frequency identification) technology, having availability in many fields based on adopted methods.
FIG. 1 is a diagram shown for describing a location recognition method using a signal strength according to the prior art.
Referring to FIG. 1, a tag 30 at any point obtains a signal strength through signals received from surrounding beacon apparatuses 10a˜10c, and transmits an obtained signal strength per beacon to a beacon apparatus 10c. 
A server 50 stores any position information from a beacon apparatus 10c (in advance known to the server as position information of a tag) and the signal strength of that position in a database.
That is, the server 50 beforehand builds a database by matching all possible positions to signal strengths of these, and estimates a corresponding position matched to a signal strength through a retrieval when inputted with the specific signal strength from the tags 10a˜10c. 
As described above, a location recognition method of the prior art gathers data using a specific sample-oriented tag in establishing a database, in which for a reception sensitivity of all tags may not be identical, an error per tag occurs. Also, in a wide space environment, it takes relatively long hours to gather data and thus time and cost, in proportion to this, extend. In addition, considering in terms of an RF charateristic, an intensity of signals can vary on its property due to seasons or atmospheric conditions, the existing technology cannot help newly builing up a database each time using a specific sample-use tag. This is considerably irrational in an aspect of time and cost.